In oil and gas wells, it often becomes necessary to stimulate hydrocarbon flow in order to attain economical feasible production rates, or to increase production rates. The technique frequently used to stimulate wells in such a manner is termed “fracturing”, and refers to a method of pumping a fluid into the well until the pressure increases to a level sufficient to fracture the subterranean geological formation, resulting in cracks in the formation. These cracks are capable of carrying product to the well bore at a significantly higher flow rate, particularly from so-called “tight” formations such as shale basins (e.g. Marcellus, Haynesville, etc).
In general, proppants are extremely useful to keep open fractures imposed by hydraulic fracturing of a subterranean formation, e.g., an oil or gas bearing strata. Typically, the fracturing is desired in the subterranean formation to increase oil or gas production. As noted above, fracturing is caused by injecting a viscous fracturing fluid, foam, or other suitable fluid at high pressure into the well to form fractures. As the fracture is formed, a particulate material, referred to as a “propping agent” or “proppant” is placed in the formation to maintain the fracture in a propped condition when the injection pressure is released. As the fracture forms, the proppants are carried into the well by suspending them in additional fluid or foam to fill the fracture with a slurry of proppant in the fluid or foam. Upon release of the injection pressure, the proppants form a “pack” which serves to hold open the fractures. The goal of using proppants is to increase production of oil and/or gas, and other hydrocarbons such as natural gas condensates, by providing a highly conductive channel in the formation.
Coatings for proppants are known, for example coatings to improve proppant thermal stability for high temperature/pressure applications, see U.S. Pat. No. 8,770,294; for improving proppant compressive strength, see U.S. Pat. No. 8,852,682; for improving proppant back flow, see U.S. Pat. Nos. 8,003,214 and 8,133,587; and for removing contaminants, such as heavy metals, see U.S. Pat. No. 8,763,700.
It is desirable to inject one or more oil well treatment agent within the fracturing fluid and proppant mixture which impart useful chemical properties (e.g., scale inhibition, corrosion inhibition, wax inhibition, and/or pour point depression, to name a few) to the production fluids coming out of the formation. Unfortunately, many such oil well treatment additives are not compatible with the fracturing fluids or foams. One solution to the solubility issue is adding a dispersion of treatment agents adsorbed on an adsorbent media, see U.S. Pat. Nos. 7,686,081 and 8,883,695. However, adding additional components increases the number of components added to the fluid/foam resulting in additional compatibility and handling/storage considerations.
Notwithstanding these various approaches, the interest in developing an efficient and cost effective way to add oil well treatment agents, especially pour point depressants and/or wax inhibitors, with proppants in oil well recovery operations remains strong.